A stricter limit on the number of people allowed to gather in a house in England is expected, in response to the surge in Covid-19 cases.
The government is examining whether to significantly cut the current figure of 30 – but has yet to decide what the new restriction would be.
It would be the first nationwide response to the spike in new coronavirus infections, which are now running at nearly 3,000 a day across the UK.
In England, only people from two households can meet in a home – theoretically up to a limit of 30 – with fines of £100 for breaching the rules, rising to £3,200 for further offences.
Anyone meeting people from more than one other household should meet outdoors, in a group of 6 people or fewer.
And, even inside someone’s home, people have been told to continue to socially distance from anyone not in their household or bubble, washing hands and surfaces frequently, while keeping windows open for ventilation.
It comes as Jonathan Van-Tam, the deputy chief medical officer, warned coronavirus must be taken seriously again or the UK will face “a bumpy ride over the next few months".
Speaking on Monday after a “big change” in infections, Professor Van-Tam warned the public had “relaxed too much” over the summer and described the rising number of cases as a “great concern”.
Prof Van-Tam said: "This is a big change. It's now consistent over two days and it's of great concern at this point.
"We've been able to relax a bit over the summer, the disease levels have been really quite low in the UK through the summer but these latest figures really show us that as much as people might like to say 'oh well it's gone away' – this hasn't gone away.
"And if we're not careful, if we don't take this incredibly seriously from this point on, we're going to have a bumpy ride over the next few months.
He said the rise is "much more marked" in the 17-21 age group, but noted there is a "more general and creeping geographic trend" across the UK.
"People have relaxed too much," Prof Van-Tam said. "Now is the time for us to re-engage and realise that this is a continuing threat to us."
He urged politicians and public health officials to think about how to manage the crisis not in the short term but through "the next six months and how we get through this until the spring".
The professor added that it was "clear" that the level of compliance with restrictions "is very variable indeed".
Similarly, Professor John Edmunds, who is part of the government's Scientific Advisory Group for Emergencies, warned that cases were "increasing exponentially".
He said the UK has entered "a risky period" with the average number of people an infected individual spreads the virus to, known as the reproduction number, above the crucial figure of one.
"I didn't want us to relax measures so much that we couldn't open the schools safely without it tipping the reproduction number significantly above one. And we are already above one and we've opened schools," he told ITV.
Meanwhile, Caerphilly in south Wales prepared to be placed under local lockdown and stricter measures were extended in Scotland.
People were told they cannot enter or leave Caerphilly without a reasonable excuse when new restrictions are imposed at 6pm on Tuesday.
Everyone over 11 will have to wear masks in shops, the first time the measure has been made mandatory in Wales, and meetings with other people indoors will be banned.
The south Wales borough has seen 133 new Covid-19 cases over the past seven days, equivalent to a rate of 55.4 cases per 100,000 population, giving it one of the highest rates in the UK.
Meanwhile, restrictions on household visits across western parts of Scotland were extended for a further week and expanded to also include East Dunbartonshire and Renfrewshire.
Additional reporting by PA Media
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